AU660985B2 - High activity polyethylene catalysts prepared from oxidizing agents - Google Patents

Description

F-6207-L(XC) -1 A-

CATAT

1 YSrS MPMM FTM OXCtDIZMN ANr Thbe present invetion relates to a catalyst for ethylene polymerization and =~polymerization, to a nthod for prodwlirg such a catalyst and to a process for ethy.ene polymerization and ethylene ccpolymerization with alriha-olefins. 3In particular, the present invention. relates to a high activity catalyst, and to a rathiod for preparation thereof and to a highly productive polymerization process carried CKR± With the catalyst of the invention. Thbe catalysis of the invention results in high density polyethylene (HDPE) or linear low density polyethylene (IMfPE) having an intermediate molecular weight distribution, as evidenced by values of melt f 1w ratio (MMR) [which is (I2216) of about 30-50 at a flow index (1 21) of about 7, and hav:1zq broved flow index response.

In cmmercial applications, ethylene hanippolymes and ethylene/ 1-colef ins ccpolymers with either a very narrow MWD or very broad mwD are inportant. Hwver, recently polymers with intermediate. MW~s havat been found to be iportant for blending t-wo or more polymer samples into c xmecially iportant products e.g. for film or blomwoding applications.

:20 Te two or more polymer sai~1es- which are blended into the final product each have a very different molecular weight. one saziple will usually have a relatively very high molecular weight as indicated by a HIZ'1 of about 0.4-5.01 while th)e other polymer sample will have a relatively very low mwlecular weight as indicated by a melt index (26of about 2D-2000). These polymer sarples can be prepared separately in Individual polymerization reactors or can be prepared in tandem polymerization reactors where the relatively high and low molecular weight f ractions are prepared sequentially in the polyerization process.

F-6207-L(SC-C) onie of the measures of the moleular weight distribution of the resin ir. mlt f low ratio (ME) which is the ratio of high load elt. ind3ex (H=II or 121) to malt index (12) for a given resin. %be malt flo ratio is believed to be an indication of the molecular weight distribution of the polymer, the higher the value, the broae the molecul~ar wemight distribut.ion. Rlesins having relatively low MER values, of about 20 to about 30, have relatively narrow molecular weight distribution.

Polymers having relatively high ME values, e.g. of about 70 to about 150 have a relatively br~oad mlecul1ar weight distribtioni.

onMZyqelntly, polymer with an MME value of about 30-60 are said to have an Inrtermediate mo~lecular weight distribation.

Another inportant property of a ethylene horpolymrizaLion catalyst or ethyllene/alph-a olef in copolymerization catalyst is the ability to otroml polymer molecular weight with relatively low amounts oz hydrogen in the polymerization process. Catalysts which give rise to a relatively high malt index resin under a certain set of *20 polymerization conditions is said to exhibit relatively good melt index respon~se.

Ac~cordingly, it is iuportant to provide a catzilyst cceposition capable of producing alpha-olef in polymers and copolymers having an Intermediate molecular weight distribtioni (MER vralues betwezen about 30-60).

It is an object of the present invention to provide a high activity catalyst ccxosition which produces alpiia-olef in plymers with high produtivity.

it is an additional object of the present invention to provide a catalytic process for polymerizing alpha-olef ins which yields polyethyl(mn of an intermediate mo~lecular weight distribution at high productivity rateS.

-3- It is an additional object of the present invention to provide a catalytic process for polymerizing alpha-olefins which yields polyethylene of an intermediate molecular weight distribution with improved flow index response.

Therefore, it is the primary objective of this invention to provide a catalyst/cocatalyst system with the combination of properties providing relatively high activity an intermediate MWD and relatively good flow index response.

All three catalyst attributes are provided by the catalysts described in this invention.

A supported alpha-olefin polymerization catalyst composition of this invention is prepared in a multi-step process.

The process for catalyst production comprises: providing a slurry in a non-polar solvent of a solid, porous, preferably inorganic support having hydroxyl groups; (ii) impregnating said support having hydroxyl groups, with RMgR' compound, to form a white intermediate, which intermediate has a Mg:hydroxyl group ratio of greater than 1, wherein each of said R and R' is alkyl of 1 to 12 carbon atoms and is the same or different; 25 (iii) treating the intermediate of step (ii) with a halogen containing reagent to form a intermediate of step(iii); (iv) treating the intermediate of step (iii) with TiCI4 to form a titanium containing intermediate which has a Ti/mg ratio of preferably greater than and more preferably in the range of 0.75 to -3Acombining the titanium containing intermediate with a trialkylaluminum compound or a dialkyl aluminum hydride compound, wherein said halogen containing reagent is effective to increase the activity of a catalyst consisting of said support, said RMgR', said TiCI 4 and said alkylaluminum compound. Preferably the hydroxyl groups on the solid, porous support are reactive hydroxyl groups. The catalyst also produces polymers and copolymers.

o rJwnodelI 813492C/julier F-62OY7-L(SGC) -4having relatively an intermediate molecular, -weight distribution and ir~roved f l1w index response.

Ube polymers prepared in the preserm of the catalyst corposition of this invention are linear polyethylenes which are haitmpolymers of ethylene ar crooymers of ethylene and higher alpha-olef ins. The Polymers exhibit 'intermediate values of malt flow ratio (MMR), as ccoqared to similar polymers prepared in the presence of previoslyknwn catalyst cxzuositionis, theose disclosed by Nowlin et al., U.S. Patent 4,481,301. %bus, the polymras, prepared with the catalyst acmositions of the invention are especially suitable for the production of films by blending two or more ciipcwrnts of polyethylene of various molecular weights.

Ybreover, the catalysts exhibit Iuroved flow index response. Flow index respose of a catalyst refers to the ability of a particular catalyst to produce relatively lower molecular weight polymer than other catalysts under the same polymerization condittions. Polymer swp~les prepared frcom one such catalyst will have a relatively higher flow ind~ex value relative to polymer prepared from~ scgne other catalyst with relatively poorer f low index response. The catalysts of this inventiori exhibit relatively good f low irxdex response, produce polymer of an intermediate molecular 'weight distribuxtion at relatively high productivity.

Catalysts produc-ed according to the present invention are described below in term of the manner in which they are made.

Catalys Synthesis The carrier material is a solid, particulate, porous, preferably inorganic mterial. These carrier materials ixiclude inorganic materials, such as oxides of silion~ anid/or aluminum.

The carrier material is ised in the form of a dry pow~der having an average particle size of from abouit 1 micron to about 250 micr=n, preferably from about 10 microns to ahiut 150 micron. Tha carrier

PL

tA 1~ F-6207-L(SGC) material is alsokyorous and has a surface area of at -least about 3 squre meters per gram (2/g and _Vreferably at least about m g.The carrier material o i..e~ry t is, free of absorbed water. Drying of the carrier material can be effected by beating at about 100-C to about 1000-C, preferably at about 600-C. ttme the carrier is silica, it is tieated to at least 2001-C, .preferably about 200-C to about 850-C and mo~st preferably at about 600-C. Mhe carrier material imst have zat least scma active- hydroxyl (OH) groups to produce the catalyst omposition' of this invention.

In the most preferred emtbodimrent, the carrier is silica which, prior to the use thereof in the first catalyst synthesis step, has been dehydrated by fluidizing it with dry nitrogen or dry air and heating at abc~t 6000C for about 16 hours to achieve a surface hydroxyl group onoentration of about 0.*7 millimoles. per gram (nttols/gm). Mie silica of the mnrst preferred embodirnt is a high surface area, armrphrous silica (surface area 300 Xi 2 /gm; pore volume of 1. 659 an 1gm) ard it is a raterial marketed under the tradenames of Davison 952 or Davison ~955 byj the Davison 2iewical Division of W.R. Grace and Compan~y. e silica is in the forin of spherical particles, as obtained by a spray-drying process.

The carrier material is slurrAe- in a non-polar solvent and the resulting slurry is contacted with at least one organciiagnesium 25 composition having the mipirica4. formuila The slurry of the carrier mcaterial in the so1,1Cispeae y introdiucing the carrier ***into the solvent, preferably while stirring, and heating the mixture to about 25 to about 100 0 C, preferably to abouxt 40 to about 606C. 7he slurry is then contacted with the aforemntioned orgarvonagnesiin 30 omosition, uftile the heatbix is continued at the aforemnentioned *temeture.

7he arganaragnesiun cmpsitian has the empirical formula R.Mg R 'where R and R are the same or different C 2 -C12 alkyl. groups, preferably C 4

-C

10 alyl group!s, :mor2 preferably C 4 normal alkyl F-6207-L(SGC) grous, and most preferably both R and R are butyl grouips, and m. and n are each~ 0, 1 or 2, providing that mi n is equal to the valence of The halogen containing reagents include halogen atarsa and are soluble in~ nc-polar solvents. Preferred halogen atoms are chlorine, bircmilne ard iodine; and most pref tzhlv the halogen atoma is chlorine. These ii'lude chlorine (Cl 2 brne iodine halogen CMPcSXiKI suchi as CC1 4 1 CRCl 3 1,1,1 trichoroethane, 1, 1-dichlcroetbane and diphenl-diclormethane.

Suttable non-polar solvents are materials in which all of the reactants used herein, the organomagnesium cqposition, the halogen containing reagent and the transition metal ccapcund, arm at least pja*.ially soluble and which are liquid at reaction teirperatures.

Preferred non-polar solvents are ailkanes, such as hexcane, n-heptane, octane, nonane, and decane, although a variety of other materials *including cyo-loalkanes, such as cyclchexane, araratics, such as benzene and ethyibenzene, may also be euployed. The mot preferred non-polar solvent is iscpentane. Prior to use, the non-polar solvent should be px:ified, such as by percolation through silica gel and/or mo~lecular sieves, to ran traces of water, oxygen, polar otpouds, and other materials capable of adversely affecting catalyst activity.

In the most preferred embodiment of the synthesis of this catalyst it is iaprtarit to add only such an am=*t of the organcmagnesium conposition that will be deposited physically or chemically onto the support since any excess of the organanagnesium ccrmsition in the solution my react withi other synthesis chemicals and precipitate outside of the supoport. 2be carrier drying temperature affects the nu~mber of sites on the carrier available for the orgarxzagnesiuma a Go: corposition the higher the drying temperature the lwer the number of sites. Thus, the exact molar ratio of the organcinagriesium oapsition to the hydroxyl, groups will vary and mu~st be determined on a case-by-case basis to assure that only so muich of the crgancinagnesium caposition is added to the solution as will be

I

F-6207-L(SGC) deposited onto the su4rt without leavirx any excess of the czrjanomagnesium composition in the' solution. Fuirthermore, it is believed that 'the molar amount of the organanagnesium ccuposition deposited onto the support is greater than the molar content of thet hydrox2yl groups on the support. Thus, the molar ratios given below are intend~ed only as an approximate guideline and the exact amount of the ur ancmagnesium oapositicn in this embodient mast be controlled byr the fbaytiona1 lim~itation discussed above, it must not -be greater than that 'which can be deposited onto the support. If greater than that amount is added to the solvent, the excess may react with other ccmncus involved in the synthesis, thereby formini a precipitate outside of the support which is detrimental in the synthesis of our catalyst andl is avoided. The amount of the organjamagnesium aposition which is not greater than that deposited 3. onto the support can be determined in any conventional ronner, e.g., by adding the oryanormagnesium cqposition to the slurry of the carrier in the solvent, while stirring the slurry, until the organaniagnesium ~carposition is detected as a solution in the solvent.

For exam~ple, for the silica carrier heated at about 600 0 C, the amt of the orgarmagnesium ccarsition added to the slurry is suchi that the molar ratio of Mgj to nhe hydrcxcyl groups (OH) on the solid carrier is about 1:1 to about 3:1, preferably about 1.1:1 to about 2:1, more too. preferably about 1.2:1 to about 1.8:1 and moost preferably about 1.4:1.

The organomagnesium ccuposition dissolves in the non-polar solvent to form a solution from which the orgarxonagnesium ccnqoiticn is deposited onto the carrier.

It is also possible to add such an amount of the organomagnesium.

cuoition which is in excess of that which will be deposited onto the support, and then remove, by filtration and 'washing, any excss of the cargancmagnesium ccaposition. However, this alternative is less desirable than the most preferred emibodiment described above.

F-6207-L(SOC) -8 The slurry is contacted with at least one tansition metal ccupound soluble in the non-polar solvent. -This syntesis~ tpi onuctea at about 25 to about 65 0 C,Lpreferably at about 30 to about 55 0 C, and most preferably at about 40 to about 50 0 C. In a preferred embodiment, the amount of the transition metal cmcxAncd added is not greater than that WU~ch can be deposited onto the carrier. The emat molar ratio of I# to the tranSition metal and of the transititon metal to the hydroxyl grus of the carrier will therefore vary (deperdxr, on the carrier drying taqxrature) and mist be determined on a case-by-case bar-is. For exanpie, for the silica carrier heated at about 200 to about 850 0 C, the aiunt of the transition metal owpouxxm is such that the molar ratio of the transit-ion retal, derived fran, the transition metal crxqxoud, to the hydroxyl. groups of the carrier is about 1 to about 2.0, preferably about 1.2 to about I.8. The amouint of the transition metal camqound is also such that the molar ratio of Mg t^the transition metal is about 0.5 to about 2.0, preferably abouxt 0.7 to akAout 1. 3.

Suitable transition netal caqpour-s used herein are caxvd of 20 metals of Groups IVA, VA, VIA or VIII of the Periodic chart of the Elements, as published by the Fisher Scientific Coapany, Catalog No.

5-702-10, 1978, providing that such ccmpounids are soluble in the nonr-polar solvents. Non-lhiitig exaiiples of such ccaqcxnds are titanium and vanadium halides, titanium tetrachloride, TiCl 4 0 Vanadium tetrachloride, VCl 4 vanadium oxytridilaride, VOC1 3 titanium *and vanadium alkoxides, wherein the aflccxide moiety has a branched or *unbrarniied alkcyl radical or 1 to about 20 carbon atoms, preferably I to about 6 carbon atoms. The preferred transition metal c ipourxls are titanium onapounds, preferably tetravalent titanium ccounds. The most preferred titanium cmipound is titanium tetrachloride.

Mixtures of such transition metal ccmpounids may also be used and generally no restrictions are iitposed on the transition metal coripounds, whti ray be included. Any transition metal caxound that ray be used alone may also be used in conjunction with other transition metal ccmpouxnds.

IV zMi91 F--6207-L(SOC) 'The slurry containingq the organosagnesium contacted suppot is treated with a halogen containing reagent. The halogen -containgi reagent is effective to react with the slurry formed by contactjxg the carrier material with the organomagnesiuu oapound. Reaction is usually detectable by color chanige. The molar ratio of halogen containing reagent to ora ium can range from 0.3 to 3. The halogen containing reagent ±inelecEia from~ the group consisting of -tin (IV) chloride, iodine, iodine raonochloride, carbon tetrachloride; ,ioform; 1,1,1 trichilc::oethane; 1,1 didfloroethane and diphenyl didhlorcmethane. The temrperature of treatment with the halogen conainngreagent gout 20-60-C. The effect of this treatment step is to irnrease the activity arid flow index response of the catalyst anid produce a polymer with an intermediate molecular weight distriburtion as indicated by Melt Flow Ratios of 30-60.

After synthesis of the precursor is ccqpleted, the non-polar solvent e N_ i slowly~ by distillation or evaporation. The t~ertureat which the non-polar solvent is remved from the synthesis mixture can affect the productivity of the resulting catalyst camsit ton. Lower solvent removal teaaperatures producea catalyst coupositions v~hich are more active than those produced with higher solvent removal terrperatures. For this reasoni, it is preferred to renm the non-polar solvent at about 40 to about 650C, preferably at about 45 to about 550C and most preferabl.y at about 550C by drying, distillation or evaporation or any other conventional means. Emress amonts of halogen containing reagent can be remorved simultaneously with the non-polar solvent(s). The excess halogen containing reagent may also be removed by filtration arnd washing the silica prior to **addition of the transition metal ccmpound.

The resulting free-.f lwing powder, referred to herein as a catalyst precursor is omxtbined with the activator. It 'was found that the cm~iaation of the pi~ecursor of this invention with the activator produces an alpha-olef in polymerization catalyst composition having very high activity, as coiqpared to a catalyst compositionxiprising F-6207-L(SGC) -1 UAsam catalyst precursor, but produced wiltho.it the treatment with halogen cotaining reagent. 1The catalyst- precursor is combined with a carventirial Ziegler-Natta catalyst activator such as aluminum alkyls or aluminum alkyl hydrides. 7he type of ac;Livat-c~ is iiirortant in c*oxlling the fl1w index response of the catalyst and the molecular 'weight distribution of the polymer. Triethylaluium (TEAL) is preferred to produce a polymer with Fk Melt Flow Patio of cabout 35-40 UhdIO diiSohxtylalmium hydride is preferred to producxe a polymer with a Melt Flow. Ratio of about 40-50. Zi-ese are referred to as polymers wit a relatively intermediate molecular weight distribution.

Vie activator is used in an amount: which is at least effective to pronmote the polymerization activity of the solid catalys-t oqixoent of tbi-t: invention. The azmnt of the activator is lffcent to give an Al:*Ti molar ratio of about 15a1 to about 1000:,\referablY about 20:1 to about 300:1, and most preferably about 25:1 to about 100:1.

Withotxt Wishing to be bound by any theory of operability, it is believed that the catalyst cauposittion of thi-s Invention is produced P h emdicallY frpregnating the suPPort with cataIyst ccmPOnents sequentially added to the slurry of the carrier in the non-polar solvent. Therefore, all of the catalyst synthesis cheiic ingredients nist be soluble in the non-polar solvent used in the synthesis. The orer of addition of the reagents may also be iuptant since the catalyst synthesis procedure is predicated on the dv~ica1 reaction between the chemical ingredients se'~metially aWZ..

to the non-polar solvent (a liquid) and the solid carrier niateria4 i a catalyst intermedIiate supported by such a material (a solid). Thu, reaction is a solid-liquid reaction. For excaiple, the catalyst synthesis procedure iiust be conduicted in such a manner as to avoid the reaction of two or more reagents In the mon-polar solvent to form a reaction product insoluble in the non-polar solvent outside of the pores of the solid catalyst support. Suich an insoluble reaction product wmuld be incapable of reacting with the carrier or the catalyst intermediate and therefore wcuild not be incorporated onto the solid support of the catalyst craprxsition.

F-62O7-L(SGC) -11-1 TIhe catalyst precarsors of tle present liwer A are prepared in the su~bstantial. abenc of water, oxygen, and other catalyst poisons.

Bixii catalyst Poisons can be exclided during the catalyst prepara~tion Steprs by any Well )now methods, by carrying out the prepmration under an atmosphav of nitrogen, argon' or other inert gas. An inert gas Purget can serve the dual Porpose of excludiing exterral cattaminants during the preparation and remo~ving undesirable reaction bY-Prodix~ts resulting b=u the preparation of the neat, liquid reaction product. Purification of the nont-polar solvent employed in the catalyst is also helpful in this regard.

The catalyst may be activated in situ by adding the activator and catalyst Separately to the 1,olynerization meium. It is also possible to cmine the catalyst and the activator before the introduction thereof into the polymerization medium, for up to about 2 hours prior to the introduction thereof into the Polymerization medim at a teperature of fromn about -40 to about 1000C.

Alpha-olef ins are polyfferized with the catalysts prepared acxoordir to the Present invention by any suitable Pro'cess. Such prooesses 1nmlude Polymerizations carried out in suspension, in solution or in, d-e gas Ph~ase. Gas Phase Polymerization reactions are preferred, those takng lac instirred bed reactors and, especially, fluidized bed reactors.

Then nolecular weight of the polymer iwvy be controlled In a knowvn mannver, by using hydrogen. With the catalysts produced aco=.Tring to the present invention, molecular weight Pay be suitably controlled with hydrogen when the polymerization is carried out at relatively low~ teqperatuxes, fromu about: 30 to about 1050C. This control of molecular weight may be evidenced by measurable positive donrq in nelIt irdex (1 2) of. the polymer produced.

F- 62 7-L W3 C) 1 Mie 7mlecular weiht distribution of the polymers prepared in tIe presence of thie catalysts of the present Lvention, as e3pressed by the MMIF values, varies frczu about 30 to 160, at HEM rarqing frcau 0-.

to 40,000. preferably, the MM1F values vary frcm~ about 35 to about for 1U'pE prochrts having a density of about 0.930 to about 0.960 g/cc, and a flow index 121.6) -of about, 0. 2 to about 20. As is kniown to thorve skillod in the art, such NFR ,values are indicative of a re3.ative3y intermediate molecular weight distribution of the polymer.

MM~ is defined herein as the ratio of the high load relt index (MU or 121) also called Flow Irdex divided by the melt index 121 12 1jaier HNR values indicate relatively more narrow mlecular weight distribution polmrs.

The catalysts prepared according to the present invention are highly active and may have an activity of at least about 1500 to about 5000 grams of polymer per gram of catalyst per 100 psi of ethylene in about 1 hour.

The inear polyethylene po1yrrp- prepre -in accrxranoe with the present 3ivention are hmriapol, 'rs of ethylene or opolyners of ethylene with one or more C 3 -Cl, 1 alpa-olief.±us. .nus, copolYmers having two monomeric units are possible as well as terpolymers having three m~orv-tric units. Particular examples of such polymers includie ethylene/1-jxtene Copolymers, ethylene/1-hxe copolymers, ethylene/l-octerva copolymers, ethylene/4-methyl/1-pentene copolymers, ethylene/l-butene/ I-hexene terpolymers, ethylene/propylene/ 1-hooene terpolymers and ethYlene/prOPYlen/l-butene terpolymrs. 7he most pre.ferred, cacn in 1-hexene.

[he high density polyethylene polymers produced in aacxordance withtlmb present invention preferably co~ntain at least about 80 percent by weight of ethylene units.

F-6207-L(SGC) 13 A particularly desirable method foar producing high density polyethylene polymers according to the present invention is in a fluid bed reactor. Such a reactor and means for operating it are described in U.S. Patent No. 4,011,382; U.S. Patent 4,302, 566; and U.S. Patent 4,481,301. The polymer produced in such a reactor contains the catalyst particlesr because the catalyst is not separated frcmu the polymer.

Preferably, in accordance with this invention, bimodal ethylene polymer blends having a desirable coabination of processability and mechanical properties are produoed by a process including the steps of polymerizing gaseous moncaneric ccmpositions oomprising a major proportion of ethylene in at least two gas phase, fluidized bed reactors operating in the tandem mode under the following conditions.

15 In the first reactor, a gas comprising mnomreric composition and, ptionally, a small amount of hydrogen, is contacted under polymerization conrditions with a catalyst of the invention, at a hydrogen/ethylene molar ratio of no higher than about 0.3 and an ethylene partial pressure no higher than about 100 psia such "20 as to produce a relatively high molecular weight (HMW) polymer powder wherein the polymer is deposited on the catalyst particles. The HMW polymer powder containing the catalyst is then transferred to a second reactor with, optionally, ;additional activator (or cocatalyst) which nay be the same or different frmn the cocatalyst utilized in the first reactor but with •no additional transition metal catalyst ccuponent, together with a gaseous mixture caaprising hydrogen and mononeric coeposition wherein additional polymerization is carried out at a hydrogen/ethylene molar ratio of at least about 0.9, the ratio being sufficiently high such 30 that it is at least about 8.0 times that in the first reactor, and an ethylene partial pressure at least 1.7 times that in the first reactor, to produce a relatively low molecular weight (INN) polymer much of which is deposited on and within the RW polymer/catalyst particles from the first reactor, such that the fraction of MW polymer in the bimodal polymer leaving the second reactor is at least about 0.35.

F-6207-L(SGC) 14 The foregoing conditions provide for a process wherein the production of fines tending to foul coaqressars and other equipment is kept to a relatively low level. Moreover, such conditions provide for an inhibited level of productivity in the first reactor with a resulting increased level of productivity in the second reactor to produce a bimodal polymer blend having a favorable melt flow ratio (MFR, an indication of molecular weight distribution) and a high degree of homogeneity (indicated by low level of gels and low heterogeneity index) caused by a substantial degree of blending of HW and IM? polymer in each final polymer particle inherently resulting from the process operation. The bimodal blend is capable of being processed without undue difficulty into films and containers for household industrial chemicals having a superior combination of mechanical properties.

The gaseous moncmer entering both reactors may consist wholly of 4 ethylene or may couprise a preponderance of ethylene and a minor a*amount of a camonamer such as a alpha-olsfin containing 3 to about carbon atoms. The oomoncmer may be present in the moonomeric 20 cc positions entering either or both reactors.

In many cases, the moncner camposition will not be the same in both reactors. For example, in making resin intended for high density film, it is preferred that the monomer entering the first reactor contain a minor amount of comoncmer such as 1-hexene so that the IHM cuponent of the bimodal product is a copolymer, whereas the mmnamer fed to the second reactor consists essentially of ethylene so that the IM couponent of the product is substantially an ethylene hroqpolymer.

When a oaioncter is employed so as to obtain a desired copolymer in 30 either or both reactors, the molar ratio of ocmonaner to ethylene may be in the range, for example, of about 0.005 to 0.7, preferably about 0.04 to 0.6.

Hydrogen may or may not be used to modulate the molecular weight of the HM polymer made in the first reactor. Thus, hydrogen may be fed to the first reactor such that the molar ratio of hydrogen to ethylene F-6207-L (SGC) (1 2

/C

2 ratio) is, for exanple, up to about 0.3, preferably about 0 to 0.2. In the second reactor it is necessary to produce a IM polymer with a low enough molecular weight and in sufficient quantity so as to produce a bimodal resin which can be formed, with a minim= s of processing difficulties, into end use products such as films and containers for hAcUsehold industrial cheicals having a superior combination of techanical properties. For this purpose, hydrogen is fed to the second reactor with the ethylene containing mormier such that the hydrogen to ethylene role ratio in the gas phase is at least about 0.9, preferably in the range of about 0.9 to 5.0 and most preferably in the range of about 1.0 to 3.5. Moreover, to provide a sufficient difference between the molecular weights of the polymers in the first and second reactor so as to obtain a bimodal resin product having a wide enough molecular weight distribution necessary for the desired levels of processability and mechanical prcerties, the hydrogen to ethylene mole ratios in the two reactors should be such :that the ratio in the second reactor is at least about 8.0 times the ratio in the first reactor, for exarple in the range 8.0 to 10,000 times such ratio, and preferably 10 to 200 times the ratio in the 20 first reactor.

Utilizing the hydrogen to ethylene ratios set out previously to obtain the desired oleclar weights of the RM and IMW polymers produced in to the first and second reactors respectively tends to result in relatively high polymer productivity in the first reactor and relatively low productivity in the second reactor. This tends to result in turn in a bimodal polymer product containing too little IM polymer to maintain satisfactory prooessability. A significant part of this invention lies in the discovery that this effect can be 30 largely erume by employing ethylene partial pressures in the two reactors so as to reduce the polymer productivity in the first reactor and raise such productivity in the second reactor. For this purpose, the ethylene partial pressure employed in the first reactor is no higher than about 100 psia, for example in the range of about 15 to 100 psia, preferably in the range of about 20 to 80 psia and the ethylene partial pressure in the second reactor is, for example in the F-6207-L(SGC) -1 range of about 26 to 170 psia, preferably about 45 to 120 psia, with the ethylene partial pressures in any specific process being suchi that the ratio of ethylene partial pressure in the second to that in the first reactor is at least about 1.7, preer-ably about 1.7 to 7.0, and more preferably about 2.0 to If desired for any purpose, to control stperficial gas. velocity or to absorb heat of reactionk, an inert gas such as nitrogen may also be present in one or both reactors in additioni to the monoer ard hydrogen. Thus the total pressure in both reactors nay be in the range, for exairple, of about 100 to 600 psig, preferably about 200 to 350 psig.

T[he temperature of polymerization in the first reactor ray be in the range, for exampl1e, of about 60 to 130 0 C, preferably about 60 to 900C, while the temperature in the second reactor may be in the rane, for example, of about 80 to 1300C, preferably about 90 to 1200C. For the purpose of controlling molecular weighit and produtivity in both o reactors, it is preferred that the tarperature. in the second reactor be at least about 106C higher, preferably aboult 30 to 600C higher than that in the first reactor.

The residerie tine of the catalyst in each reactor is controlled so 0 that the p-oductivity is suppressed in the first reactor and~ enIiaied in the second reactor, consistent with the desired properties of the bircdal polymer product. Thus, the residence time may be, for example, about 0. 5 to 6 hours, pref erably about 1 to 3 hours in the first reactor, and, for exanple, about I to 12 hours, preferably about to 5 hours in the second reactor, with the ratio of residence tize 30 in the second reactor to that in the first reactor being in the range, for example, of aboat 5 to 0.7, preferably about 2 to 1.

The stperficial gas velocity through both reactors is sufficiently high t-o disperse effectively the beat of reaction so as to prevent the tiamerature frcm risixj to levels 'Which could partially melt the polroer and hut the reactor damn, and high enctgh to maintain the F-M07-L(SGC) 17 interity of the fluidized beds. Such gas velocity is in the range, for example, of about 40 to 120, preferably about 50 to 90 cm/sec.

Uhe productivity of the process in the first reactor in terms of grams of polymer per gram atcm of transition metal in the catalyst multiplied by 106, mey be in the range, for example, of about 1.6 to 16.0, preferably about 3.2 to 9.6; in the seoord reactor, the productivity may be in the range, for example, of about 0.6 to 9.6, preferably about 1.6 to 3.5, and in the overall process, the productivity is in the range, for example, of about 2.2 to 25.6, preferably about 4.8 to 16.0. The foregoing ranges are based on analysis of residual catalyst metals in the resin product.

The polymer produced in the first reactor has a flow index (FI or 1211 measured at 190 0 C in accordance with ASIM D-1238, ondition for exreile, of about 0.05 to 5, preferably about 0.1 to 3 grams/10 min.

and a density in the range, for exanile, of about 0.890 to 0.960, "preferably abut 0.900 to 0.940 grams/c.

20 The polymer produced in the second reactor has a melt index (MI or 12, measured at 1906C in accordance with AMIM D-1238, Cordition E) in the range, for example, of about 10 to 4000, preferably about 15 to 2000 grams/O rain. and a density in the range, for example, of about 0.890 to 0.976, preferably about 0.930 to 0.976 grams/cc. Miese values are calculated based on a single reactor process model using steady state *process data.

0 *ee.

The final granular bimodal polymer frc= the seond reactor has a weight fraction of EW polymer of at least about 0.35, preferably in the range of about 0.35 to 0.75, 1ore preferably about 0.45 to 0.65, a •flow index in the range, for example, of about 3 to 200, preferably about 6 to 100 grams/10 rin., a melt flow ratio (MFR, calculated as the ratio of flaw index to melt index) An the range, for example, of about 60 to 250, preferably about 80 to 150, a density in the range, for examle, of about 0.89 to 0.965, preferably about 0.910 to 0.960, F-6207-L(SGC) 18 an average particle Size (APS) in the range, for exaiPle, Of about 127 to 1270, Preferably about 380 to 1100o miacrns, and a fines content (defined as particles 'which pass through a 120 nesh screen) of less than about 10 weight Percent, Preferably less than about 3 ,ieit paxcet. With regard to fines content, it has been found that a very IOW aMirt Of fines are produced in the first (IWB) reactor and that the percentage of fines changes very little across thes secord reactor.

71"i is aurprising since a relaeively largje aii~ut of fines are Pro ie 'Alel the first Or only reactor in a gas Viase, fluidized bed systel 1'3 used to Produce a relatively 1ow molecular weight (T"W polymer as defined herein. A probable explanation for this is that in t110 Process of this invention, the flAw polyzer formed in the second reactor deposits prinarily within the void structure of the IH pojymr particles produced in the f ist reactor, minimizing the focrmation Of IMW fines. This is indicated by an increase in settled *..*bulk density (SED) across the second reactor 'while the APS stay.

fairly constant.

Wnen pellets are formed fromn granular resin 'which was -stabilized and 'COMCOined with two passes on a Brabeixler extrudier to ensure uniform blendin, such pellets have a flow index in the range_, for ample, of about 3 to 200, preferably about 6 to 100 g=6n/1Q min., a welt flow ratio in the rangle, for exanpie, of about 60 to 250, preferably abouit 80 tD 150, and a heterogeneity index (BI, the ratio of the F1 Is of the granlar to the pelleted res-in) in the range for exanple of about ~tG Preferably about 1.0 to HI indlicates the relative tjegree of inter-particle heterogeneity of the granular resin.

The follWi'ig EcamPles illustrate the invention.

Thbe properties of the polymers produced In the Th5mples were deterined~ by the following test nethods: Melt Index 12 ASWM D-1238- ondition E Meaured at l90oc reported as grams per minutes.

F-6207-L(SGC) 19 High Load Melt Index ASTM D-1238 Condition F Measured (HEM) 121 at 10.5 times the weight used in the melt index test above.

,21 Melt Flow Ratio (MR) 12 Productivity The polymer produced in one hour in a slurry polymerization reactor is weighted and divided by the weight of the catalyst precursor added to the reactor. The data is normalized to 100 psi of ethylene pressure.

15 EXAMNPLES Catalyst Preparation All manipulations were conducted under a nitrogen atmosphere by using standard Schlerik techniques. Into a 200 ml Schlenk flask was placed granms of Davison grade 955 silica, which was previously dried under a nitrogen purge at 600°C for about 16 hours. Hexane (90 ml) was added to the silica.

""Dibutylmagnesium (7.0 rmol) was added to the stirred slurry at 50-55 0

°C

and stirring was continued for one hour to produce white product, A halogen containing reagent (9.2 nrool) was added to the slurry (50-55°C) and stirring was continued for one hour during which time o 0 the color usually changed from white to brown. TiC1 4 (7.0 rnmol) was added to the reaction flask (50-550C) and stirring was continued for an additional hour. Hexane %.as then removed by distillation with a 30 nitrogen purge at 50-55°C. Yield varied frau 8.0-9.3 grams depending on the halogen containing reagent employed.

Polymerization Ethylene/l-hexene copolymers were prepared with these catalysts under the same polymerization conditions. A typical example is shown below.

F-6207-L(SGC) 20 A 1.6 liter stainless steel autoclave under a slow nitrogen purge at 0 °C was filled with 750 ml. of dry hexane, 30 ml of dry 1-hexene, and mmol of triethylaluminum. The reactor was closed, the stirring was increased to 900 rpm, and the internal temperature was increased to 85°C. The internal pressure was raised 12 psi with hydrogen.

Ethylene was introduced to maintain the pressure at about 120 psi.

Te internal temperature was decreased to 80aC, 20.0 mg of catalyst was introduced into the reactor with ethylene over-pressure, and the internal texperature was increased and held at 850C. The polymerization was continued for 60 minutes, and then the ethylene supply was stopped and the reactor was allowed to cool to room terperature. The polyethylene was collected and air dried.

Given below are the catalyst productivities and polymer flow indexes 15 and melt flow ratios (I21/I2). The catalysts were prepared acoording to the sequence.

DBM Oxidizing Agent TiCl 4 Silica EK. Co- Flow H(2) No. Halogen Reagent Productivity Catalyst Index (Psi) MFR 1 None (Control) 590 TEAL 2.4 12 70.1 2 tin (IV) chloride 3830 TEAL 3.8 12 30.9 3 iodine 3240 TEAL 9.3 12 38.0 25 4 iodine monochloride 3680 TEAL 6.0 12 38.3 e. 5 carbon tetrachloride 4660 TEAL 7.4 12 35.8 6 carbon tetrachloride 3405 TEAL 11.7 14 34.3 7 carbon tetrachloride 4160 DIBAH 8.7 '14 48.7 8 carbon tetrachloride 3065 TEAL 416 76 30.5 9 carbon tetrachloride 3100 DIBAH 720 76 36.9 g polyethylene/g catalyst/hr/100 psi ethylene hydrogen pressure in polymerization reactor Productivity is given in units of g/g-h-100 psi ethylene.

F-6207-L(SGC) -2 It*e data show that the use of an oxidizing agent (exen~1es 2-9) suhetantially increases the produoctivity of the catalyst.

Hiest productivity was obtained with the carbon tetrach).aride-based catalyst. 2me use of a halogen containing s reagent in the preparation of the catalyst also resulted in polymer with a narrower molecalar weight distribution relative to a catalyst (exmiple 1) prepared wit'o,=t the halogen containing reagent as indicated by the low FR values-. T1he catayst prepared with iodine gave polymer with the highest flow indlex (highest Flow Index Response) under our Polymerization conditions. The catalysts of this invention all edAibit betier f low index response relative to the catalyst prepared without thc halogen cantaining reagent.

ThMrple 7 shca; that diisobutylaluminuit hydride (DIBMI) as cocatalyst provides h1-igher activity and produce-- polymer with a broader HMD than the polymer produced with TML as cocatalyst (example With high levels of hydrogen in the reactor (examrples 8 and 9) DIBAH also provides a higher Flow Index polymer.

The interaction of silics with dibutylmagnesium (DM4) an oxi~dizing agent, and Tim1 4 produces a high activity olef in polymetrization catalyst in the presence of the occatalyst.

triethylaluminm. The u~se of the halogen containing reagent greatly increases the activity of the catalyst, rarrcws the polymer itolecular weight distribution, and iyqroves the f low index response of the catalyst.

Claims (15)

1- A~n ethylenle hcanoolymerization or ocolymerisation catalyst for producing polymer) 20=o 5 uhich catalyst is formned by .providing a slurry of a solid poxrous support having3 -Mi grotps. and a non-polar solvent; (11) imrenating the support having MT groups with W ocaq.xond to form an interm~ediate, which intermediate has an -CH %roup:Mg ratio of less than 1, wherein each of R and which may be the same or different, represents an alkyl group of 1 to 12 carbon atcmns; (111) treating the intermediate withi TIC]. 4 to form a' titanium containing interediate whlich has an -MU giLoAp:Ti ratio of less than 1; cobining the titanium containing intermediate with an aluminum coupound as a cocatalyst,. werehl intermediate of stAVp (ii) is treated with an amount of halogen cnt--aning reagent which is soluble in the non-polar solvent and is reactive with the intermediate of step (ii) and A~ich amunt is effective to provide an halogen ocritainirgj reagent:MpR', mmla ratio frcyn 0.3 to 3 and the I I I 4m!*d=dth triethylalumiqum or dilsoutylaluminum hydride, whereby thrIR is from 30 to 60 at-) of 0.1. to 40,000.

2. A .catalyst according to Claim 1, wherein the halogen containing reagentke*zeitin (IV) chloride, chlorine, bromine, iodine, iodine m~ohloride, carbon tetrachloride; chloroform; 1,1,1 trichloroethane; 1,1 dictloroethane; diphenyl dichloromethane or a mixture thereof. A cataljyst conposition acording to claim 1 or 2, whterein R gn R are C 4 -CIO alkyl groups. w.

F-6207-L(SGC) 2-

4. A catalyst capr 'tc to any preceding claim, wherein the nmn-polar solvent cvisa& hydrocarbon whL- is a ILeiid at aubiezrt ond~itions.

A catalyst comosition aacoding to any preceding claim, wherein the amount of the TIC1 4 present in step (iii) is such that the mo~lar ratio of Vq to Ti is frcM 0.5 to 2.

6. A catalyst coupoition according to clain 5, wherein the armxt of the TICl 4 present in step (iii) is such that the molar ratio of D4 to Ti is from. 0.75 to

7. A catalyst ccloosition according to any preceding claim, wherei~n the amount of the ac .,ancanagnesium camition used in step is such that the iwolar ratio !ig:oH is frcm 1:3. to about 3:1.

8. A catalyst cczx5csition alcazdirq to any preceding claim, wherein Sthe solid, porous carrier \silica which, prior to contact thereof with the solvent in step is heated at a tesperature. of at .20 least 200 0 C.

9 A catalyst c1Tposition according to claim 8, wherein the silica has, after heating, a surface hydroxyl group concentration of about 7 mmoles/g, a surface areaL of about 300 ),,7/9ram, and a pore volume of about 1.65 m 3/gram.

A catalys according to any preceding claim, wherein the abxiin .OMMF4earr-.QW\tiethylalutum and the F is 35 to 40 or hydride and the MFR is 40 to

11. An ethylene homppolyimrization or copolymer! 'ition process Whch process ewpw corltacting a feed canzr" ethylene, under ethylene hco: o-Iyuixizattion or copolymerize' in coryvMitions, with a catalyst formed by prvid.i~g a slurry of a solid porous support having -OH groups and a non-polar solvent; 24 (ii) impregnating the support having -OH groups with RMgR' compound to form an intermediate, which intermediate has an -OH group:Mg ratio of less than 1, wherein each of said R and which may be the same or different, represents an alkyl group of 1 to 12 carbon atoms; (iii) treating the intermediate with TiC14 to form a titanium containing intermediate which has an -OH group:Ti ratio of less than 1; (iv) combining the titanium containing intermediate with an aluminum compound as cocatalyst, wherein the intermediate of step (ii) is treated with an amount of halogen containing reagent which is soluble in the non-polar solvent and is reactive with the intermediate of step and which amount is effective to provide an halogen containing reagent:RMgR' molar ratio from 0.3 to 3; the cocatalyst is triethylaluminum or 25 diisobutylaluminum hydride; and polymer product is recovered which has a melt flow ratio (MFR) from 30 to 60 at high load melt index (HLMI) of 0.1 to 40,000. 30

12. A catalytic process for producing bimodal polyethylene homopolymer or copolymer, which process includes polymerizing gaseous monomeric compositions including a major proportion of ethylene in at least two gas phases, in the tandem mode, wherein in a first phase, a gas including monomeric ethylene and, optionally, a small amount of hydrogen, is contacted under polymerization conditions with a catalyst, at a hydrogen/ ethylene molar ratio of up to 0.3 and an ethylene partial S3?4 \pressure up to 100 psia such as to produce a relatively 25 high molecular weight (HMW) polymer powder wherein the polymer is admixed with the catalyst; and wherein, the HMW polymer powder containing the catalyst is then transferred to a second phase together with a gaseous mixture comprising hydrogen and ethylene wherein additional polymerization, in said second phase is carried out at a hydrogen/ethylene molar ratio of at least 0.9, the ratio being sufficiently high such that it is at least 8.0 times that in the first phase, and an ethylene partial pressure of 1.7 times that in the first phase, to produce a relatively low molecular weight (LMW) polymer, such that the fraction of HMW polymer in the bimodal polymer leaving the second reactor is at least 0.35, wherein the catalyst controls the molecular weight distribution of polymer product as determired by melt flow ratio (MFR), wherein the catalyst is formed by providing a slurry of a solid porous support having -OH groups and a non-polar solvent; (ii) impregnating the support having -OH groups Swith RMgR' compound to form an intermediate, which intermediate has an -OH group:Mg ratio of less than wherein each of said R and which may be the same or different, represents an alkyl group of 30 1 to 12 carbon atoms; (iii) treating the intermediate with TiCl4 to form a titanium containing intermediate which has an -OH group:Ti ratio of less than 1; (iv) combining the titanium containing intermediate with an aluminum compound as cocatalyst, wherein treating the intermediate of step 25A (ii) is treated with an amount to halogen containing reagent which is soluble in the non-polar solvent and is reactive with the intermediate of step and which amount is effective to provide an halogen containing reagent:RMgR' molar ratio fro m0.3 to 3; the cocatalyst is triethylaluminum or diisobutylaluminum hydride; and polymer product is recovered which has a melt flow ratio (MFR) from 30 to 60 high load melt index (HLMI) of 0.1 to 40,000.

13. A process according to Claim 12, wherein monomer in the first phase contains a minor amount of comonomer so that the HMW component of the bimodal product is a copolymer, wherein the gaseous mixture to the second phase consists essentially of ethylene so that the IMW component of the produce '3 substantially an ethylene homopolymer.

14. A process according to any of claims 11 to 13 wherein the catalyst is as defined in any of claims 1 to

15. A catalyst according to claim 1 substantially as 25 hereinbefore described with reference to any one of Examples 2 to 9. SDATED: 6 FEBRUARY, 1995 PHILLIPS ORMONDE FITZPATRCIK "Attorneys for: c MOBIL OIL CORPORATION •o• F-6207-L(SGC) 26 ABSIRACV A supported alpha-olefin polymerization catalyst composition of this invention is prepared in a m.lti-step process. The process for catalyst -production comprises providing a slurry in a non-polar solvent of a solid porous inorganic suport havinq reactive hydroxyl groups; (ii) impregnating said support having hydroxyl groups, with I3R' cazmpound, to form a white intermediate, which intermediate has a Mg:hydroxyl group ratio of greater than 1, wherein each of said R and R' is alkyl of 1 to 12 carbon atoms and is the same or different; (iii) treating the intermediate of step (ii) with a halogen containing reagent to form a brown intermediate of step (iii); 46 (iv) treating the intermediate of step (iii) with TiC 4 to form a titanium containing intermediate which has a Ti/Mg ratio of greater than 0.5; caonbining the titanium containing intermediate with a trialkylalumimnum cmpound or a dialkyl aluminum hydride ccanpund,wherein said halogen containing reagent is effective to increase the activity of a catalyst consisting of said support, said RMgR', said TiCl 4 and said alkylaluminum comnpound. The catalyst also produces polymers and copolymers having relatively an intermediate molecular weight distribution and improved flow index response.